The biodegradation of phenyl propanoids is important for the global carbon cycle from an environmental point of view, since these compounds are released from plant wastes as breakdown products from lignin. With the improvement of living conditions, demand for natural or green products has increased. In contrast to chemical synthesis, biological methods have the advantages such as mild reaction condition, fewer byproducts, less environmental pollution, selectivity and simpler downstream processing. However, in most reported cases, the transformation yields are very low and only a few of them are cost effective for commercial production. Much scientific interest has been focused on the ability of micro organisms to metabolize the hydroxy cinnamic acids such as ferulic acid, p-coumaric acid, caffeic acid, sinapic acid into hydroxy benzoate derivatives which are of commercial importance.
Para-hydroxy benzoic acid and its derivatives are widely used as preservatives by cosmetic and pharmaceutical industries. For example para-hydroxy benzoic acid is effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bactericidal and fungicidal properties. They can be found in shampoos, commercial moisturizers, shaving gels, personal lubricants, topical/parenteral pharmaceuticals, spray tanning solution, makeup, and toothpaste. They are also used as food additives.
Cultures of S. sannanensis when grown on minimal medium containing ferulic acid as sole carbon source, vanillic acid accumulation was observed in the medium as the major biotransformed product along with transient formation of vanillin. A maximum amount of 400 mg/L vanillic acid accumulation was observed, when cultures were grown on 5 mM ferulic acid at 28° C. This accumulation of vanillic acid was found to be stable in the culture media for a long period of time, thus facilitating its recovery (Microbial transformation of ferulic acid to vanillic acid by Streptomyces sannanensis MTCC 6637 J Ind Microbiol Biotechnol (2007) 34:131-138)
Sporotrichum thermophile is capable of promoting the formation of vanillic acid during ferulic acid degradation. Ferulic acid metabolism by S. thermophile apparently occurred via the propenoic chain degradation and the formation of 4-hydroxy-3-methoxystyrene (4-vinylguaiacol) was observed which was presumably metabolized to vanillic acid. (Bioconversion of ferulic acid into vanillic acid by the thermophilic fungus Sporotrichum thermophile Lebensm.-Wiss. u.-Technol. 36 (2003) 561-565). Guaiacol was detected in addition to the above-mentioned intermediates, usually as a result of nonoxidative decarboxylation of vanillic acid. Under optimum conditions vanillic acid production from ferulic acid by S. thermophile attained very high levels of 4798 mg/L with a molar yield of 35%.
Biotransformations of cinnamic and ferulic acidl catalyzed by actinomycetes have been studied. Strain GE 107678, identified as Streptomyces halstedii, converted cinnamic acid in cinnamamide (95% molar conversion from 2 g/L of substrate) and ferulic acid in vanillic acid (80% molar conversion from 1 g/L of substrate) with transient formation of low amounts of vanillin (0.10-0.15 g/L). Strain GE 107678 resulted the most promising, since it was able to convert cinnamic acid into the corresponding amide with high yield (Biotransformations of cinnamic and ferulic acid with actinomycetes Enzyme and Microbial Technology 34 (2004) 3-9).
The enzymatic formation of p-hydroxybenzoic acid from p-coumaric acid has been detected in cell free extracts of Lithospermum erythrorhizon cell cultures. In the absence of NAD, p-hydroxybenzaldehyde is formed instead of p-hydroxybenzoic acid. The reaction is specific to p-coumaric acid. In addition, a p-hydroxybenzaldehyde dehydrogenase activity is also found. The results suggest that the reaction mechanism is non-oxidative (Formation of p-hydroxy benzoic acid from p-coumaric acid by cell free extract of Lithospermum erythrorhizon cell cultures Phytochemistry, Volume 30, Issue 7, 1991, Pages 2233-2236).
Cell suspensions of Acinetobacter calcoaceticus strain DSM 586 and DSM 590 were able to grow on benzoic, p-hydroxybenzoic and vanillic acid as sole carbon source. Cells induced with trans-ferulic acid were able to oxidize trans-ferulic, p-coumaric, vanillic, p-hydroxybenzoic and protocatechuic acid at rates higher than the uninduced culture. The same activity was found in the p-coumaric acid induced culture. Two aromatic compounds, vanillic and p-hydroxybenzoic acid, were isolated from culture filtrates of trans-ferulic and p-coumaric acid grown cells, respectively (Degradation of trans-ferulic acid and p-coumaric acid. Biochim Biophys Acta. 1995 Jun. 9; 1244 (2-3):363-7).
Streptomyces setonii strain 75Vi2 was grown at 45° C. in liquid media containing yeast extract and trans-cinnamic acid, p-coumaric acid, ferulic acid, or vanillin. Cinnamic acid was catabolized via benzaldehyde, benzoic acid, and catechol; p-coumaric acid was catabolized via p-hydroxybenzaldehyde, p-hydroxybenzoic acid, and protocatechuic acid; ferulic acid was catabolized via vanillin, vanillic acid, and protocatechuic acid. When vanillin was used as the initial growth substrate, it was catabolized via vanillic acid, guaiacol, and catechol (Can J Microbiol. 1983 October; 29(10:1253-7).
U.S. Pat. No. 6,844,019 discloses use of Pseudomonas putida to convert ferulic acid to vanillic acid, wherein the process of the invention converted 28.5 g/L ferulic acid to 19.05 g/L of vanillic acid with an overall yield of 91.48% and a conversion rate of 84.38% after 160 hrs by fed batch method.
Another U.S. Pat. No. 6,844,019 discloses the use of Rhodotorula glutens to convert p-coumaric acid to p-hydroxy benzoic acid. 2.1 g/L of p-hydroxy benzoic acid was obtained from 4 g/L of p-coumaric acid. 3,4-dihydroxybenzoic acid was also obtained as byproduct in the concentration of 0.47 g/L. The process was gave 62.39% yield and 97% conversion.
U.S. Pat. No. 5,866,380 employs Aspergillus niger MIC 373, wherein ferulic acid was added in continuous fashion in doses of 0.430 g/L per 24 hrs. After 15 days, 5.05 g/L ferulic acid was consumed, 3.6 g/L vanillic acid and 0.109 g/L MHQ was produced. Yield of vanillic acid was 82%.
Another U.S. Pat. No. 5,866,380 also employs the Actinomycete streptomyces setonii ATCC 25497, wherein ferulic acid was added in the concentration of 1 g/L. After 100 hrs, 0.88 g/L ferulic acid was consumed, and 0.332 g/L vanillic acid was produced. Molar yield of vanillic acid was 43%.
US20060292676 employs Aspergillus niger CGMCC 0774 to convert ferulic acid to vanillic acid. A solution of rice bran oil was added in proportion of 10g/ 100 ml of culture. The concentration of ferulic acid in the culture was 2.02g/100 ml, was subjected to hydrolysis by fermentation at temperature of 37° C. for 24 hrs. The final concentration of ferulic acid and that of vanillic acid was 1.22 g/100ml and 0.68 g/100 ml respectively.